Ratios between acute aquatic toxicity and effects on population growth rates in relation to toxicant mode of action
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Abstract Environmental risk assessment of chemicals is mostly based on the results of standardized toxicity tests. To obtain environmental quality criteria, extrapolation factors are used that depend on the amount and quality of available data. These extrapolation factors do not, however, take into account the mode of action of the compound tested or the life history of the test organism. In this study, we analyzed the variability in acute‐to‐chronic ratios (ACRs) for various chemicals in relation to their mode of action. Chemicals were classified as nonpolar narcotics, polar narcotics, specifically acting compounds, and heavy metals. As an acute endpoint, the LC50 was used; as a chronic endpoint, the lowest test concentration at which the natural rate of population increase ( r ) is affected, or LOEC( r ), was used. Data were derived from the on‐line literature. Nonpolar narcotic chemicals demonstrate the smallest variation in ACRs, and acute tests can be used to derive chronic endpoints for this class. For the other classes, the variation in ACRs is larger. Fish species especially show a relatively large ACR. For heavy metals, differences in the mode of action may play an important role in explaining differences in ACRs. For the other three classes, however, it is less reliable to predict chronic toxicity using the results of acute tests. In general, differences in species sensitivity rather than in mode of action for the chemical seem to determine differences in ACRs.Keywords:
Toxicant
Mode of Action
Chronic toxicity
Abstract Environmental risk assessment of chemicals is mostly based on the results of standardized toxicity tests. To obtain environmental quality criteria, extrapolation factors are used that depend on the amount and quality of available data. These extrapolation factors do not, however, take into account the mode of action of the compound tested or the life history of the test organism. In this study, we analyzed the variability in acute‐to‐chronic ratios (ACRs) for various chemicals in relation to their mode of action. Chemicals were classified as nonpolar narcotics, polar narcotics, specifically acting compounds, and heavy metals. As an acute endpoint, the LC50 was used; as a chronic endpoint, the lowest test concentration at which the natural rate of population increase ( r ) is affected, or LOEC( r ), was used. Data were derived from the on‐line literature. Nonpolar narcotic chemicals demonstrate the smallest variation in ACRs, and acute tests can be used to derive chronic endpoints for this class. For the other classes, the variation in ACRs is larger. Fish species especially show a relatively large ACR. For heavy metals, differences in the mode of action may play an important role in explaining differences in ACRs. For the other three classes, however, it is less reliable to predict chronic toxicity using the results of acute tests. In general, differences in species sensitivity rather than in mode of action for the chemical seem to determine differences in ACRs.
Toxicant
Mode of Action
Chronic toxicity
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Chronic toxicity
Aquatic toxicology
Daphnia magna
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Chronic toxicity
Narcotic
Daphnia magna
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Chronic toxicity
Bioconcentration
Aquatic toxicology
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Abstract Determining the value of a half-effective or half-life concentration or dose of toxicant is the main purpose of acute toxicity studies, and this is also the most commonly used value in the toxicity characteristics of substances. By conducting tests that meet the criteria and requirements for the determination of acute toxicity, due to the use of appropriate mathematical tools and concentrations resulting in complete lethal effects in the studied groups, considerably more important values can be achieved, which give a possibility for the analysis of the entire process’s dynamics, as well as determining the threshold values of the effect time and toxicant concentration. This was the purpose of our research, in which the research species were Daphnia magna and Cypris pubera . The effect of the conducted research allowed to determine and compare the two toxicants: ammonium and copper(II) ions by it’s: concentration limit values ( C th ), internal toxicity of the receptor-ligand complex ( α ), apparent, constant disintegration of this complex ( K app ) and different time values of the effect ( T t , T in , MLT ), which, along with concentration, is equally important determinant of the development of a toxic effect.
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Daphnia magna
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The use of internal concentrations as a dose parameter for baseline toxicity requires an understanding of the relationship between accumulation level and toxic effects, not only for acute but also for chronic exposure. In this study of chronic toxicity of the nonpolar narcotic 1,2,3,4-tetrachlorobenzene (TeCB) to Chironomus riparius, the chronic median lethal concentration (LC50) was determined to be 0.99 (0.54-1.82) microM, the median sublethal effect concentration (EC50) for growth was 0.76 (0.73-0.97) microM, and the chronic (sublethal) no-observed-effect concentration (NOEC) was 0.24 +/- 0.01 microM. An acute-to-chronic ratio of 9.8 was calculated from a previously determined acute LC50 value and this NOEC. The chronic critical body residue (CBR), 136 mmol/kg lipid, was the same as the acute CBR, previously determined. The similarity of the chronic and acute CBRs lends support to the exposure time independent aspect of baseline toxicity theory. An implication of this is that internal concentrations estimated by biomimetic sampling devices may be compared to acute CBR data to determine chronic baseline toxicity risk. Such sampling devices, solid-phase microextraction (SPME) fibers, were simultaneously exposed during the toxicity test. The results of this study suggest that body residues estimated with SPME may be used to predict baseline toxicity for various exposure durations.
Chironomus riparius
Narcotic
Chronic toxicity
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Acute toxicity of 25 narcotic compounds to D. magna was determined in this paper. Acute/ Chronic Ratios (ACRs), which are often used to estimate chronic toxicity from acute toxicity data, are discussed based on Quantitative Structure‐Activity Relationships (QSARs) of the compounds between both acute and chronic toxicity data and n‐octanol/water partition coefficients, and an improved equation is derived to estimate chronic toxicity data from acute toxicity data. Application of the improved equation and ACRs is illustrated for D. magna and fathead minnow to estimate chronic toxicity from acute toxicity.
Chronic toxicity
Daphnia magna
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The determination of the chronic toxicity is time-consumed and costly, so it's of great interest to predict the chronic toxicity based on acute data. Current methods include the acute to chronic ratios (ACRs) and the QSTR models, both of which have some usage limitations. In this paper, the acute and chronic mixture toxicity of three types of antibiotics, namely sulfonamides, sulfonamide potentiators and tetracyclines, were determined by a bioluminescence inhibition test. A novel QSTR model was developed for predicting the chronic mixture toxicity using the acute data and docking-based descriptors. This model revealed a complex relationship between the acute and chronic toxicity, i.e. a linear correlation between the acute and chronic lg(-lgEC50)s, rather than the simple EC
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Environmental risk assessment of chemicals is mostly based on the results of standardized toxicity tests. To obtain environmental quality criteria, extrapolation factors are used that depend on the amount and quality of available data. These extrapolation factors do not, however, take into account the mode of action of the compound tested or the life history of the test organism. In this study, we analyzed the variability in acute-to-chronic ratios (ACRs) for various chemicals in relation to their mode of action. Chemicals were classified as nonpolar narcotics, polar narcotics, specifically acting compounds, and heavy metals. As an acute endpoint, the LC50 was used; as a chronic endpoint, the lowest test concentration at which the natural rate of population increase (r) is affected, or LOEC(r), was used. Data were derived from the on-line literature. Nonpolar narcotic chemicals demonstrate the smallest variation in ACRs, and acute tests can be used to derive chronic endpoints for this class. For the other classes, the variation in ACRs is larger. Fish species especially show a relatively large ACR. For heavy metals, differences in the mode of action may play an important role in explaining differences in ACRs. For the other three classes, however, it is less reliable to predict chronic toxicity using the results of acute tests. In general, differences in species sensitivity rather than in mode of action for the chemical seem to determine differences in ACRs.
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Aquatic toxicology
Mode of Action
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Toxicant
Mode of Action
Chemical toxicity
Mechanism of Action
Mode (computer interface)
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